1. Field of the Invention
The present invention relates to a semiconductor device, and is suitably usable for a semiconductor device having a structure capable of reducing unnecessary wave (spurious) of a transmitting unit, for example.
2. Description of the Background Art
Mobile communication devices such as mobile phones, personal digital assistants (PDAs), WiFi® (Wireless Fidelity) transceivers, and other communication devices transmit/receive communication signals in various frequencies.
In particular, in a mobile phone or the like, an LTE (Long Term Evolution)/W-CDMA/GSM® triple mode transceiver or the like has been used.
For efficient communication, transmission and reception signals have frequencies several times higher than baseband information signals that carry information to be communicated. Accordingly, each of such transceivers has to up-convert a transmission signal and down-convert a reception signal using a frequency modulator.
In response to a request for downsizing, such a transceiver is frequently formed as one chip. Accordingly, circuits of the transmitting unit and the receiving unit may cause generation of noise in the receiving unit and the transmitting unit, respectively. In particular, due to an influence of magnetic field generated by current flowing in each circuit, current is induced in the other circuit, disadvantageously. As a technique for preventing such noise, the following techniques have been disclosed.
Japanese Patent Laying-Open No. 2004-228144 (Patent Document 1) has an object to implement a structure capable of suppressing inductors from being deteriorated in properties due to magnetic coupling between the inductors in an array-type coil component including a plurality of coils. In the coil component of the invention disclosed in Japanese Patent Laying-Open No. 2004-228144 (Patent Document 1), a plurality of coils are disposed in a stacked member, which includes insulator layers stacked on each other, such that they are adjacent to each other in a direction perpendicular to the stacking direction. Each of the coils is formed of a linear conductor and has a substantially spiral shape or substantially helical shape. Between adjacent coils, linear conductors close to and opposite to each other have extended lines substantially orthogonally crossing each other on the same surface of the insulator layer.
Japanese Patent Laying-Open No. 2005-327931 (Patent Document 2) has an object to provide an integrated inductor capable of suppressing self-mixing resulting from coupling between integrated inductors, and allowing for simplification of circuit and reduction of chip size and power consumption, as well as a receiving circuit employing such an integrated inductor. In the invention disclosed in Japanese Patent Laying-Open No. 2005-327931 (Patent Document 2), at least two conductor layers are provided on a substrate. First and second inductor units are provided which have helical shapes, are formed of the first conductor layer, and are disposed adjacent to each other. The first and second inductor units are connected to each other such that a direction of current in the first inductor unit is opposite to a direction of current in the second inductor unit. For connection between an external circuit and each of the first and second inductor units, the second conductor layer provides at least two portions crossing the first conductor layer.
In particular, an in-phase component (common mode) of a signal generated from a local oscillator of a receiving unit is leaked to a frequency converter of a transmitting unit, i.e., is leaked to a quadrature modulator, and is mixed with the third harmonic of the transmission wave to result in generation of spurious.
The leakage of the signal generated by the local oscillator of the receiving unit is caused by magnetic coupling between a horseshoe-shaped inductor of the oscillator of the receiving unit and a spiral-shaped inductor of the quadrature modulator.
For example, in the case where a transceiver operates at a Band 1 (transmission frequency: 1920 MHz to 1980 MHz; reception frequency: 2110 MHz to 2170 MHz), this unnecessary wave (spurious) falls to a GPS band (1575.42 MHz=3*1955 MHz−2*2145 MHz; the frequency of the signal generated by the local oscillator of the receiving unit is twice as large as the reception frequency). This causes deterioration of reception sensitivity of a GPS receiver provided on the same substrate, disadvantageously.
In the prior art, Japanese Patent Laying-Open No. 2004-228144 (Patent Document 1), the two inductors are arranged such that their “L-shaped” portions face each other, thereby reducing leakage of a signal between the inductors irrespective of in-phase component or differential component. However, Japanese Patent Laying-Open No. 2004-228144 does not fully contemplate to reduce unnecessary wave (spurious) when the in-phase component (common mode) is leaked to the spiral-shaped inductor.
Meanwhile, in Japanese Patent Laying-Open No. 2005-327931 (Patent Document 2), 8-shaped inductors are used for the local oscillator and a low noise amplifier of the receiving circuit, thereby reducing interference between both the circuits. However, Japanese Patent Laying-Open No. 2005-327931 does not fully contemplate to reduce unnecessary wave (spurious) when the in-phase component (common mode) is leaked to the spiral-shaped inductor.